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<div class="titlepage"><div><div><h3 class="title">
<a name="boost_asio.reference.asio_handler_invoke"></a><a class="link" href="asio_handler_invoke.html" title="asio_handler_invoke">asio_handler_invoke</a>
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<p>
        <a class="indexterm" name="idp30058464"></a> 
Default invoke function for handlers.
      </p>
<pre class="programlisting"><span class="keyword">template</span><span class="special">&lt;</span>
    <span class="keyword">typename</span> <span class="identifier">Function</span><span class="special">&gt;</span>
<span class="keyword">void</span> <span class="identifier">asio_handler_invoke</span><span class="special">(</span>
    <span class="identifier">Function</span> <span class="identifier">function</span><span class="special">,</span>
    <span class="special">...</span> <span class="special">);</span>
</pre>
<p>
        Completion handlers for asynchronous operations are invoked by the <a class="link" href="io_service.html" title="io_service"><code class="computeroutput"><span class="identifier">io_service</span></code></a>
        associated with the corresponding object (e.g. a socket or deadline_timer).
        Certain guarantees are made on when the handler may be invoked, in particular
        that a handler can only be invoked from a thread that is currently calling
        <code class="computeroutput"><span class="identifier">run</span><span class="special">()</span></code>
        on the corresponding <a class="link" href="io_service.html" title="io_service"><code class="computeroutput"><span class="identifier">io_service</span></code></a> object. Handlers may
        subsequently be invoked through other objects (such as <a class="link" href="io_service__strand.html" title="io_service::strand"><code class="computeroutput"><span class="identifier">io_service</span><span class="special">::</span><span class="identifier">strand</span></code></a> objects) that provide additional
        guarantees.
      </p>
<p>
        When asynchronous operations are composed from other asynchronous operations,
        all intermediate handlers should be invoked using the same method as the
        final handler. This is required to ensure that user-defined objects are not
        accessed in a way that may violate the guarantees. This hooking function
        ensures that the invoked method used for the final handler is accessible
        at each intermediate step.
      </p>
<p>
        Implement asio_handler_invoke for your own handlers to specify a custom invocation
        strategy.
      </p>
<p>
        This default implementation is simply:
      </p>
<pre class="programlisting"><span class="identifier">function</span><span class="special">();</span>
</pre>
<h5>
<a name="boost_asio.reference.asio_handler_invoke.h0"></a>
        <span><a name="boost_asio.reference.asio_handler_invoke.example"></a></span><a class="link" href="asio_handler_invoke.html#boost_asio.reference.asio_handler_invoke.example">Example</a>
      </h5>
<pre class="programlisting"><span class="keyword">class</span> <span class="identifier">my_handler</span><span class="special">;</span>

<span class="keyword">template</span> <span class="special">&lt;</span><span class="keyword">typename</span> <span class="identifier">Function</span><span class="special">&gt;</span>
<span class="keyword">void</span> <span class="identifier">asio_handler_invoke</span><span class="special">(</span><span class="identifier">Function</span> <span class="identifier">function</span><span class="special">,</span> <span class="identifier">my_handler</span><span class="special">*</span> <span class="identifier">context</span><span class="special">)</span>
<span class="special">{</span>
  <span class="identifier">context</span><span class="special">-&gt;</span><span class="identifier">strand_</span><span class="special">.</span><span class="identifier">dispatch</span><span class="special">(</span><span class="identifier">function</span><span class="special">);</span>
<span class="special">}</span>
</pre>
<h5>
<a name="boost_asio.reference.asio_handler_invoke.h1"></a>
        <span><a name="boost_asio.reference.asio_handler_invoke.requirements"></a></span><a class="link" href="asio_handler_invoke.html#boost_asio.reference.asio_handler_invoke.requirements">Requirements</a>
      </h5>
<p>
        <span class="bold"><strong>Header: </strong></span><code class="literal">boost/asio/handler_invoke_hook.hpp</code>
      </p>
<p>
        <span class="bold"><strong>Convenience header: </strong></span><code class="literal">boost/asio.hpp</code>
      </p>
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<td align="right"><div class="copyright-footer">Copyright &#169; 2003-2012 Christopher M. Kohlhoff<p>
        Distributed under the Boost Software License, Version 1.0. (See accompanying
        file LICENSE_1_0.txt or copy at <a href="http://www.boost.org/LICENSE_1_0.txt" target="_top">http://www.boost.org/LICENSE_1_0.txt</a>)
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